How do you greet a demigod? If you're in Yorkshire, the answer's obvious - with a brass band. As Amitabh Bachchan steps off the red carpet on to platform four of York station amid a platoon of minders and gophers, the local Rail Band strike up a fully burnished version of 'There's No Business Like Showbusiness'.

It's a singularly appropriate sentiment. Bollywood's biggest star is in town, or rather county, to bang the drum for next year's International Indian Film Academy awards (IIFAs) which will be held in Sheffield. If the former steel capital seems an improbable setting for a celebration of Bombay glitz, Yorkshire tourism, local commerce and a vast audience of British Asians reckon otherwise. Thanks to the Indian diaspora, the sub-continent's cinema is now a global commercial force - Indian films now gross more at the UK box office than our homegrown product. Where there's Bolly, there's brass.

As 'brand ambassador' for the IIFAs, Bachchan is a gilded asset, a name that can garner a House of Commons launch and a 30-minute audience with Gordon Brown. Dressed in a plaid Armani coat that sets off his trademark silver goatee, the 64-year-old actor still cuts an imposing figure as he strides across York station to a silver Rolls-Royce the size of a small tank, though not all the locals are impressed. 'Never heard of him,' comes one loud, deadpan twang.

Hundreds of millions have, though: in 1999 Bachchan was the surprise winner of a BBC poll for the stage or screen superstar of the millennium, a result he disarmingly ascribed to 'computer error'. At home, 'the Big B' is inescapable. In India's teeming cities his face looms down from every other billboard, either advertising his latest film - in India, a dozen movies a year is considered normal - or raising a glass for Pepsi. Then there is his role as host of Kaun Banega Crorepati, the Indian Who Wants to Be a Millionaire?, the country's most popular TV programme, with an astonishing 250m-strong audience.

It's small wonder that Bachchan is revered by many Indians as a sub-deity, a status that he attributes to his country's religiosity. 'Many of the stories in our films are drawn ultimately from our mythology and our religion,' he tells me when I catch up with him at the IIFAs' northern launch in Bradford, an event that attracts enough local dignitaries to crew an ocean liner and a crowd of adoring mums and daughters outside. 'So in the cinema a transformation takes place and we become King Ram or the evil Raman.'

Later he will sum up his extraordinary success and status differently: 'God has been kind. The people have been kinder.'

Bachchan's ascent to the top of the movie pantheon has involved a mixture of chutzpah and controversy. His career took off in the early Seventies, when he played a corruption-busting cop in Zanjeer, followed by a succession of roles as action hero and 'angry young man', notably in 1975's epic 'curry western' Sholay (he is about to star in a remake, this time as a bandit boss). While such parts cast Bachchan as an amalgam of Eastwood and Connery, he also had the obligatory song-and-dance routines - hence a characteristic incarnation in a Saturday Night Fever-style white suit, but brandishing an automatic, 007 style, while a tousled temptress sprawls at his feet.

'Our films are demanding for an actor,' he points out, 'because we have to do action, comedy and dance.' Even now, when he customarily plays the benign patriarch, he is expected to shake an onscreen leg.

A brush with mortality after a 1982 screen stunt misfired left him in a coma while the nation waited for news. Soon after came an ill-judged entry into politics in 1985 in support of his boyhood friend Rajiv Gandhi. It was, says Bachchan, a 'purely emotional' decision following the assassination of Rajiv's mother Indira, then Prime Minister. Bachchan lasted a scant couple of years in politics - 'I just didn't know the game' - while attempts to implicate him in scandal led to a lengthy media boycott that was lifted only after his screen career revived in the late Nineties.

Bachchan's closeness to the Gandhi and Nehru dynasties reflects his upper-crust heritage. Unusually for one of Bombay's film world, which despite its popularity is often viewed as a den of iniquity, the actor is from a scholarly family. His father, a celebrated poet, was the first to translate Shakespeare into Hindi. Something of a bard's eloquence flutters around Amitabh and his mesmeric, purring baritone.

In the way of Indian cinema, he and his actress wife Jaya have spawned a dynasty of their own; their son Abhishek has become a star in his own right, and is rumoured to be marrying Aishwarya Rai, Bollywood's ruling princess (perhaps the one Indian actor whose name resounds among western audiences). Bachchan smiles. 'Yes, I have heard that rumour, too,' he twinkles abruptly.

Ironically for a big-screen star, it's the small screen that helped resurrect Bachchan's career, after a slump in the Nineties following a series of poorly received films. 'Crorepati has been some kind of a wonder,' he says. 'For me, it's an opportunity to meet the common man, to know about his life, his feelings. These are things that don't normally happen to film actors. Three days after the show started I went on a pilgrimage to a Shiva shrine up in the Himalayas. I went by helicopter, otherwise it takes five days to get there, and there were cave people shouting "Crorepati" at me.'

Bachchan reckons that the escalation of television over the past dozen years is driving cinematic change. 'The numbers are incredible - there's a population of a billion, and three-quarters of them watch TV. When you talk about a top TV show in the west having 11m viewers - one city in India will take care of that. We have 250m for one programme!' The qualitative effect is being seen in the cinema, too, he says: 'If someone is watching quality stuff from the west on television, they don't want something of a lesser standard at the movie theatre. The younger generation of filmmakers is conscious of that.'

Perhaps, but apart from being more slickly shot, most of Bollywood's prodigious output - at a thousand films a year, it's twice that of Hollywood - still looks desperately thin. When I took a tour of Mumbai's studios and cinema lots in 2002, it seemed that Indian cinema and the west might be moving into a new confluence. Lagaan was in contention at the Oscars (it was trumped by Bosnia's No Man's Land), Bombay Dreams was on stage in London and Broadway, and Moulin Rouge, a Bollywood musical in French drag, was a hit. With the deregulation of laws restricting foreign investment in the country's films, a new breed of Indian film looked inevitable.

Thus far it hasn't arrived - Bombay has continued to turn out its traditional pabulum while the only western audiences paying attention are the so-called NRIs (Non-Resident Indians) whose dollars and pounds wield so much power. This year's smash, Kabhi Alvida Naa Kehna ('Never Say Goodbye'), which stars Amitabh alongside Shahrukh Khan (Mumbai's Cary Grant), took £2m in five weeks in the UK (the same gross as, say, Vera Drake) but to critical indifference. Bollywood's song and dance numbers have enormous charm and vigour, but the paper-thin plots, daft dialogue and fairy tale settings are, at best, an acquired taste, especially over three hours.

When I put this to Bachchan, he is, as ever, the arch-diplomat. 'The revenues have increased markedly, whether the white audience has been able to see our films I'm not sure, but the numbers have increased. It's a process that will take time. Obviously there is the language barrier, but Indian cinema has made an impact - and I'm talking here about the escapist commercial cinema which has often been the subject of great ridicule and cynicism. That very content is now gaining acceptability - I never imagined people in the west would be scrutinising our work with so much intelligence. '

The problem facing Indian filmmakers is that if they compromise Bollywood conventions, especially the sanitised depiction of romance and family life, they will lose their core audience, one which must embrace both the multiplexes of Bangalore's Silicon Valley and the ramshackle cinemas of India's dirt poor rural community, where most of its huge population still lives.

'We have our own traditions that we are keen to hang on to,' says Bachchan. 'Every time we have tried to make something too smart it has failed.'

Yet one wonders how long the new India that is soaking up western culture as never before will settle for escapism. This, after all, is a society where sex outside marriage seems not to officially exist, where screen kisses are still censored, but which has one of the most alarming rates of Aids in the world.

Bachchan regards the forces of global commerce and secularisation with equanimity. 'We have a very rich past stretching back 5,000 years, and our ethics, our morals have not undergone any great change. Our stories continue to be about the family union,' he says, 'the mother-son relationship, festivals, sacrifice, stories that are rooted in myth and an enduring culture.'

Bachchan also takes just pride in cinema's role as a cultural bond for a country where the divisions of religion have often run deep and dark. 'In a society that is so diverse it's the one entity that is integrated. It's truly secular, it binds people together rather than sets them apart. We have never discriminated against any class, creed or religion. For example, three of our topmost stars are Muslim' - the (unrelated) Khans, Shahrukh, Salman and Aamir - 'and some of India's most patriotic songs have been written by Muslims. We have never propagated violence. When we sit together in the theatre we never ask whether the person next to us is Muslim, Christian, Hindu or Sikh. It's a wonderful amalgam.'